Grindstone



W. H. M GILL May 7, 1935.

GRINDSTONE Filed Sept. 24, 1934 2 Sheets-Sheet 1 Fig.2

May 7, 1935. w. H. MCGI L 2,000,772

GRINDSTONE Filed Sept. 24, 1934 2 Sheets-Sheet 2 v INVENTOR.

Patented 7, 1935- a 'This invention mm to grindingiwheels or grindstones of the tyne made or natural. stone. It "is more especially concemed with the grind stones used in grinding wood'in the process of The stones used in pulpgrindin'glrnachines are substantially cylindrical in form andof relativee' ly large. dimensions; us'ually running'fr'om fiftyg four {to sixty-seven inches in diameter and'fro'xri twenty-.four: to fifty-four inches I in wi'dth i f Theyare of two general typest one made from natural stone and the other-from artiflcial' 'abra siv'e 'mate'rial of somesuitable characten su'ch as silicon carbide, orfthe' like. The Y forrner hav the advantage of producingEa -btter grade of pulp but? the latter" give a higher" rate ofpro;

duction and have greater mechanical strength. i

The present v invention aims 'toz'devise a grindstone in which the advantages oftlies'e' twofltypes ('lfstones'will combinmlfifl x; 1 1 :1

" The nature of'the invention will be readily understood from the iollowingdescription when re'ad; in. connection with' the facco fpanyin drawings and the novel features 'willb'e'j'p'articw glarly pointed; out in the .abpended clairnsl In th'e'kdrawings Fig. :1 'is* men view or "pulp grindsftoiie constructed in Y accordance with] this I invention i 211s a :plan' .view fof the st'one'fshovvn in Figs.- 3, 4 a d '5 are. angular views illustrating additionalembodiments of'th e-invent'ionf- I V Referring first to Figs. 1* and 2;, thegrindingb wheel or stone! there shown cionsis't's' otnatural stone but hasd-a'multiplicity of inserts in the form oi dowelsi setinto'it radially: *Th esein sorts flnreierably' are made of "an artificial abra sive, such a's silicon'carbide r-ammi noq xi'de, infa' more or less-iinelyidividedgiormfthe par: ticles" being united by. some suitable binder. 'Or some of the-various grades of emery, garnet or quartz maybe used. So far as the composi tion an'd methods of manufacture of these elements are concerned, the prior practices may be I followed. In other words, these'jinserts may be made of the same-compositions andby the-same methods heretofore used in the-manufacture of. grinding wheels, and the like, from carborundum and other artificial abrasives; The inserts may. be molded to' the desired shape'and dimensions,

the binder cured, and the completed inserts then placed-in holesdrilled inthe stone 2 and cerite being commohformsfi nge'nei'al; the

, g A -further mented securely '{in theiri{i Opera, rvef'positi Or; the" composition'ingits 'p l'astjic state may be-;- I forced into th'eihbles insthefstone andftheston may later'be b'aked'to 'oiire' thfefbinder. The

practice 'to' be followed in anyfparticularfcase necessarily willjf vary "with ithe requirements fof individual situations. Various waterproof d hesivesinaf be used to' c em ent fthe in'serts in their sockets, such as 'sodiu'm sili'catefba lite,

and some of the synthetic-"resins haviii ee q siv P p t e l btal an" D; f l

ers' usedin the: composition of'ftheinserts makef satisfactorycexnentsjior sfecuring the' n -jT If serts 'in the stone. v ;Dowels may readily'fbe made' of such fcoxnp tions as-"those'above described'which will have I considerably greater tensile strength thanfidoes the isan'dstone' from which these grindstones arei cut. 3 Consequently by making these? dowels ='of suitable dimension s, sayior examfile 'two' on'thrjee V making them long enoughf to" extend subsitana tially through' the wearing voluine' ofg'the sage; the strength of the stoneagainst breakage whiie inoperation can be increased -very substantially. Usually; these dowels need n'otbe over' seven or eight inches 'in} length; They should be st'agf *gredJsOmewht taS--shown* in Fi -.f; 2 so' 'thaitf this abrasive material will; be distributed sub; s'tantially uniformly over the workingifs urfai ce 1 may be produced by 'ifmiregnatin g the fstdn .with' a waternroof binder, preferably-ofa'resln?- 1 ous natuij a's disclosed in my earlier Patent No. 1 ,'959,05 9. ,---If the,samevbinder-islalso used,

' in the composition 01 the insertsthen the em. ;w1 1 odabove describedyin whichtheintroduced 'ele 3 L .gnent shre'forcedinto the cavitie's inthe' 'stdne while inj-ar plastic condition, "i'sff'greatly 1m n: tated sincethis operationcambeperformed-at the "conclusion" of tlie impregnating step and v the entire stone may {then ;be *reacted ito' f con 3 vert the impregnating and-binding jagents into their solid; vinSolubli-f c oliditio n The ratio between the areas of thenatural andartificial abrasives may be variedvery con-' siderably by changing the shape, dimensions and "1 spacing of thejinserts'. At' present I' preferfthe', V r construction illustrated inFigs. 1 and 2m which rounddowels are used and are sospaced-and' dimensioned that they'formi about six: per cent r ofythe grinding or peripheral surface of v the lstone when it is new. This ratio, however, will;

increase m y, mechan sm a isa l stant peripheral speed asthelstonef wears down; Some decrease in grinding rate or production By using a'suite necessarily vary with the requirements of different grades of work, but my experiments have indicated that the proportion of artificial abrasive surface should seldom be less than five and rarely more than fifteen per cent ofthe total grinding area.

As the stone wears down the proportion of the total grinding area formed by the exposed surfaces of the inserts will increase, in the construction shown in Figs. 1' and 2.. to the fact that these inserts have a uniform diameter and their exposed area, therefore, remains constant while the grinding area of the stonegrows' smaller with the diminishing radius. This is adesirable action for the reason -that these stones are run at a fixed speed and. con.- sequently, it is impossible 'to m'aintain" a conrate thus necessarily occurs. able proportion of, an artifieial gritor abrasive having'a higher cutting rate than that of the natural stone therelative increase in area of.

this artificial abrasive resulting" from: wear increases the efficiencyl oithe' stone and thus compensates in 'some'nieasurefor the reduction The combination-of an artificial abrasive with a 1natural stonejis of further advantage in increasing theoutputobtainable from the natural stone while still preserving most of the advantage which this stone affords in quality as, comparedgwith the artificial stones This difference inyquality results chiefly from" the action know as regrinding. This means that as the stone revolves it carries fibres removed from V one bloclroi wood along under one or more on :whilchthe stone-operates. ;Thus the ,advan enlarged inner edges." These strips are inserted endwisein the slots out for them in the stone additional blocks where theafibres are'further acted .upon. In the, case-of an artificial stone this regrimling does more harm than good, because thesharp abrasive. pulverizes a large portion of the fibre andgrinds it to a flour. The natural stone, being milder in its action, does not produce this result/but improves the quality of the pulp In the composite stone shownin the drawings'most of this regrinding action, will take place on the naturalstone. At the same time the higher abrasive properties of the sharper artificial stone are utilized in effecting" the initial removaloffibre from the wood blocks tages of the two types of stones are combined.

Figs 3 illustrates. a modification in which the inserts are made in the form of plates or strips 4 and are set into slots which extend at an to the elements of the cylinder and also lie tangent to an inner circle in the cylinder.

, Fig. 4 shows-adifierent constructionlin which the inserts have-the ;form' of plates orstrips, areyp s tioned radiallyin the 1 stone, and have and are cementedinplacein'the same manner as are the dowels 3-and the inserts 4 of the forms of the invention abovedescribed. .If desired, said inner margins may be reinforced by rods or sections of wire rope, as indicated at 6.

A somewhat similar construction is illustrated in Fig. '5, the artificial abrasive strips 1 in this form of the invention, however, being tapered or somewhat dove-tailed in shape and having their greaterthicknesses located toward the axis of the stone. Both this construction and that illustrated in Fig. 4 give added mechanical security in the anchoring of the inserts in the tone, while the arrangement shown in Fig. 5

has the advantage of firm-easing more rapidly the ratio between the exposed surface area of the inserts and the total grinding area of the stone as the stone wears down.

While Lhave herein shown and described typical embodiments of my invention it will be evident thatthe invention may be embodied :in other .formswithout departing from the spirit or scope thereof.

I claim:

1. A grindingywheel of natural stone having inserts of a different abrasive-materialsecuxed therein, the surfaces of said inserts beingexposed at the grinding'iace of thestone: 2. A grinding wheel of natural stone having :lDSfiIt-S'Of a diife'rent abrasive material secured therein. inserts having greater strength than the stone and extending Jinto I said wheelrfor a sufiicient depth to substantially increasethe strength of the'wheel. 3; A grinding wheel oi natural stone having i sertsof anartiilcial abrasive material secured therein, the surfaces of said inserts being exposed atthe grinding face of the stone. i

4. Asrinding. wheel of natural stone having inserts of an artificial abrasive material secured therein, the surfacesuoi saidinserts being exposed'at thej grindingwface. of thestone and forming between 5 and 15 per centv of the grinding area of the wheel 5. .A grinding wheel of natural" stonehaving a series of molded inserts, made of finely divided artificial abrasive united by'a waterproof hinder, extending into the body of said wheel for a substantialdistance.;. I e e v I I 6. A grindinewheel of natural stone having a series of'dowels of stronger material than the through its working portion, the exposed surfaces of said inserts forming a substantialproportion of the grinding surface of the stone and saidinserts being of sueh-dimensions that the total v ercentage.jof the grinding area formed by them will increase as the stone is worn down.

7 WILLIAM, H. .McGILL,

- stone extending into the body ofthestone from 

